Positional signaling mediated by a receptor-like kinase in Arabidopsis.

The position-dependent specification of root epidermal cells in Arabidopsis provides an elegant paradigm for cell patterning during development. Here, we describe a new gene, SCRAMBLED (SCM), required for cells to appropriately interpret their location within the developing root epidermis. SCM encodes a receptor-like kinase protein with a predicted extracellular domain of six leucine-rich repeats and an intracellular serine-threonine kinase domain. SCM regulates the expression of the GLABRA2, CAPRICE, WEREWOLF, and ENHANCER OF GLABRA3 transcription factor genes that define the cell fates. Further, the SCM gene is expressed throughout the developing root. Therefore, SCM likely enables developing epidermal cells to detect positional cues and establish an appropriate cell-type pattern.